Resistance unit



"L, RElcHoLn.

RESISTANCE UNIT.

APPLICATION FILED MAR. 28, I9I9.

Patented on 25, 1921.

.Iliff/Idil,

F'igg.

Inventor:

Ludwig Reic hold,

I'I is-I ttor-neg:

' rolled like al solid metal.

' resistance conductor is a sheath wire, namely,

UNITED STATES? PATENT oFllcE..

LUDWIG -BEICHOLD, 0F PITTSFIELD, HASSACHUS'TTS, ASSIGNOR TO GENERAL :ELEC- TBIC COMPL-NY, ACORPORATION 0F NEW VYORK.Y

BESISTAN CE UNIT.

To vall/whom t may concern: Y

Be it known` that I, LUDWIG Rnrononn, a citizen of the United States, residing at Pittsfield, in the county of Berkshire, State of Massachusetts, have invented certain new andl useful Improvements in Resistance Units, of which the following is a specification.. 'y

My invention relatesl to electric heatingA elements of the type in which a resistance..

conductor is inclosed in va metallic sheath and insulated from it by a thin dense layer of insulating material. Resistance elements of' this general type are now in common use in electric heaters and the .like and are known as sheath wire elements. One of the characteristic featuresof this resistanceelement is that the insulating layer between the conductor and the sheath is very thin and yery closely compacted so that the conductor sheath. The usual method of producing such a resistance element is to locate Aa straight Vresistance conductor, whichmay be as magnesia, so as to completely embedand l2 properly center the core wire. The endst of the tube are then plugged, suitable provision being made for the ends o'f the core wire which extend beyond the tube, and the tube is subjected to a reducing process. The re` sult of this operation is the reduction of both the sheath and the core wire, with the consequent compacting of the insulating m a terial. The arrangement is such that when the core wire is reduced to its desired size, the insulating material is so thoroughly compacted that it becomes practically a unit with the vcore wire and may be drawn or Ordinarily the straight wire although it has been proposed to employ a spiral wire.

In carrying out my invention I utilize one of the characteristic features of the the compacting of the insulating material by reducing the diameter of the inclosing tube or sheath. The resistance conductor, however, is in-the formjof a spiral mounted upon a metal su The conductor is insulated from the support throughout its length but is connected sheath; Fig, 5 1s in very intimate thermal relation with .the f pport.

Specieation ofletters Patent. Patented Ot, 25, 1921, uppiieation med-umn 2s, 1919. 'serial no. 285,743.

thereto at one end so that the support car-v ries the currentV through the tube and both of the terminals are at one end. This is an advantage, especially where astraight heating unit is desired as, for instance, where the unit is vto be inserted in anopening in `the'body or article to be heated.

By this arrangement I may utili'ze'a relatively small wire of considerable length so support for the wire; Fig. 2 shows a die for applying insulating material to the core.; Fig. 3 shows the-core insulated and ready for the wire; Fig. 4 shows the wire wound on the 'core and ready for insertion in the shows the unit ready to be swaged down or reduced; Fig. 6 shows the completed` unit; Fig. 7 is a plan view of' Fig. .6; and F'g. 8 is a plan view of the die shown in Fig. 2.

Referring to the drawings, the ing 0 ,10' represents metallic core or support for the wire, beprovided with a shoulder 11 and flange his core is covered with insulating material throughout its smallest diameter. :Ihe particular process which insulating this core is shown in Fig. 2 and consists in inserting the core-in a split die 18 having an opening of the as the shoulderv portion 11.Y A metallic ferrule 14 is inserted in the die near the end of the core and the' die is then filled with .'po'wdered insulating material which ma be .magnesium oxid 'slightly moistened with a' thin solution of water and sodium silicate. The material is then compressed on the -core by the hollow plunger 15. The die is then opened and the core with the insulating material attached thereto removed and allowed to dry so as to harden the insulating material. Fig. 3 shows 'the core after .this operation has been performed. The resistance Awire is then wound upon the core, being first wound upon the shoulder vportion 11 ward separated as hereinafter pointed out.

I employ for.-

same diameter which is flush with the insulating material As shown in Fig. 4 a clamping ring 16 is inserted over the-end lof the wire so as to insure goo'd electrical contact vbetween the wire and the shoulder portion of thecore.

core and wire with a powdered material such as. dry magnesium oXid and the upwasher 19 which is later removed. The parts are now as shown in Fig. 5. The tube with the parts contained therein now undergoes a reducing process preferably by a swaging or rolling process whereby the diameter is reduced, thereby lcompressing the materiaLand lengthening the parts. The

insulating material is forcedl between the turns ofthe wire and the core 10 reduced in diameter. The material is' compacted until there is only a .relatively thin layer between the resistance wire and the sheath. I `The end of the sheath is now cut oil" so as to remove the washer 19, and acsteel washer-20 is inserted over the sleeve 14 in electrical contact therewith.` Aterminal 21 is secured tothe steel washer. A second washer 22 isinserted over the end of the core 10, there being a slot 23 provided for the passage of the terminal 21. This .washer 22 is I,heldin place by the riveting -over ofthe core 24 and a terminal 25. is secured to the washer 22. It will thus be seen that I have provided a very rugged and compact form of heating unit which is eiicientan'd conveniently arranged for insertion in bodies or articles to be heated and for'other urposes. n v

AWhile I have escribed my invention as embodied in concrete form and vas. operat-l ing in a specific manner in accordance with the provisions of the patent statutes, it

should beunderstood thatIdo not limit myv invention thereto as various modifications thereof]v will suggest themselves to those skilled in the art without departing from the spirit of my invention the scope of which is set forth in the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. The methodof making electric heating units which consists in mounting a helical resistance conductor on a support, inclosing the same in a metallic tube, filling the tube with powdered insulating material and then compacting the insulating material by reducing the diameter of the tube. I

2. The method of making an electric heating unit which consists in winding a resistance conductor upon a cylindrical core of insulating material, inclosing the same in a metallic sheath, filling the space around the i resistance conductor with powdered insulating Vmaterial and then compacting the poW-plderedmaterial by reducing the diameter of' the sheath.

3. The method fof making electric, heatingl units which consists in placing a sinuous resistance'` element mounted upon a support in a metallic sheath, filling the space around the same with heat refractory insulating material and then compacting the insulating ,material and forcing it between Ithe turns of the resistanceA conductor byreducing the 4diameter of the sheath. per end of the tube clos'ed by anauxiliary ythe support to compactV the insulating materlal.

5. The method of making electric heating units which consists in placing a sinuous resistance element mounted upon a metallic support and electrically connectedY therewith at ,one end in a metallic sheath, filling the space around the same with heat refractory insulating material and then compacting thev insulating material and forcing it between the turns of the resistance conductor by re' ducingthe diameter of the' sheath.

6. The method of making electric heating units which consists in applying powdered heat refractory tinisulating 'material to 'a metallic support, mounting a sinuous resistance element thereon, placing the support in 1a metallic sheath, filling the space around the, same with heat. refractory'insulating material and then compacting the insulating material and forcing it between the turns by reducing the diameter of the sheath.

7 The method of making electric heating units which consists in mounting a helical resistance conductor with its turns in con-l tact on a support, inclosing the same in a metallic sheath, filling the space around the same with heat .refractory insulating'material and then compacting the insulating material and forcing it between the turns of the resistance conductor by reducing the diameter of the sheath.

'8. The method of making electric heating units which consists in placing a helical con-V ductor with its turns in contact mounted upon and electrically connected at one end with a metallic support in a metallic sheath,

heat refractory insulating material to a metallic support, mounting a helical conductor with its turns in contact thereon and elec trically connecting it therewith at one end, placing said support in a metallic sheath, filling thespace around the same with heat refractory insulating material and then compacting the insulating material and forcing 1t between the turns of the resistance conductor by reducing the sheath.

10. An electric heating unit comprising a metallic sheath, powdered heat refractory insulating material compacted to a hard dense mass within said sheath, a central metallic core( therein and a' spiral resistance conductor -surrounding said core and electrically connected thereto at one end.

l1. An electric heating unit comprising a metallic sheath, a central metallic core therein, ahelical resistance conductor surrounding said core andpowdered heat refractory insulating materialrcompacted to a hard dense mass within said sheath and betweenv the turns of the resistance conductor.

with the core at. one .end and powdered heat refractory insulating materialcompacted to l a hard dense mass within said sheath and between the turns of the resistance conductor.

13. An electric heating unit comprising a metallicA sheath, powdered heat refractory insulating material compacted to a hard dense mass within said sheath, a central metallic core therein and a spiral resistance conductor surrounding said core and-spaced therefrom by said insulating material but electrically connected thereto at one end.

In witness whereof, I have hereunto my hand this 25 day of March, 1919.

LUDWIG REIcHoLD..

set 

